Not Applicable.
1. The Field of the Invention
The present invention relates to cutting tools. More particularly, the present invention relates to hydraulically and/or pneumatically actuated cutting tools.
2. The Relevant Technology
Various types of cutting tools are known for cutting branches, pipes, solid objects, and the like. Such cutting tools may range from a simple knife to tools which utilize principles of science to enhance the cutting ability of the tool. For example, pruning shears rely on principals of physics to magnify the strength of the user. However, previous cutting tools, such as pruning shears, required the user to grasp a pair of handles which required additional balance as well as strength. Thus, hydraulic devices were developed to enhance the ability of the user to cut objects without requiring so much of the user""s strength. However, present hydraulic cutting devices have various limitations.
One problem that currently exists in the art is that present hydraulic devices require a number of movable parts in order to effectuate release of pressure inside the tool. Such requirement of mechanical parts results in potential failing of the tool and is also difficult to repair. Additionally, such need for mechanical parts results in additional manufacturing costs. Thus, it would be an advantage in the art to have a hydraulic cutting tool having minimal parts and minimal manufacturing costs.
Typically, cutting devices utilize a standard garden hose, taking advantage of water pressure to actuate the cutting tool. A problem exists in the art in that present hydraulic devices are not adaptable to use various types of fluid sources. For example, a person may want to use a cutting tool in a machine shop, but does not have or does not want to use the water source that prior art devices have required. It would be an advantage in the art to be able to utilize different sources of fluid pressure to facilitate certain tasks.
An additional need that exists in the art is the ability to adjust the length and utility of the cutting tool. For example, a user may need a cutting tool of different lengths. Alternatively, a user may want to replace the cutting blade with a different attachment, but is unable to with existing hydraulic devices. It would thus be an advantage in the art to have a cutting tool which allowed the user to vary the size and type of attachment. Further, as longer attachments are used, more strength must be provided in the cutting tool to support longer attachments.
Finally, as with all cutting apparatuses, safety is always an important factor. Previous hydraulic tools did not provide the safety mechanisms desired to operate a tool safely and effectively.
One embodiment of the present invention comprises a housing having disposed therein a piston assembly. Fluid enters in one end of the housing and advances the piston assembly toward the other end. The piston assembly drives a piston rod which has a cutting blade attached at to the end thereof. A shaft houses the piston rod and provides a blade sheath into which the cutting blade slides. Once the cutting blade is advanced so as to cut a desired object, the fluid pressure behind the piston is released. A spring then returns the piston to its original position.
The piston assembly, in one embodiment, comprises a piston and a seal which is operable between two positions. In a first resting position, the seal is slightly retracted radially inward from the interior surface of the housing, thereby forming a gap between the housing and the seal. As a fluid, such as water or air, enters the housing, the seal is outwardly pressed so as to effect a biased substantial sealed engagement between interior surface of the housing and the piston. In this position, the fluid pressure builds behind the piston causing the piston assembly to advance within the housing, thereby advancing the cutting blade within the blade sheath. When the applied fluid pressure is released, the seal resiliently returns to its original resting position. Fluid behind the piston is then able to escape through the gap formed between the seal and the housing. As the fluid escapes, the spring resiliently biases the piston back into its original position.
The present invention provides a number of different embodiments for allowing the seal to function in the two operable positions. The seal may be disposed in an annular groove in the piston. Pressure from the fluid is channeled onto the seal to force it outward against the interior surface of the housing. In another embodiment, a plate may be used to force the seal against the interior surface of the housing. Still in other embodiments, the pressure of the fluid may independently serve to force the seal against the interior surface of the housing.
The present invention also provides for safe operation of the cutting tool and provides for a tool that is light-weight. The cutting tool may operate hydraulically or pneumatically. The operator can also use a number of different attachments and lengths of attachments on the end of the cutting tool.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.